1. Field of the Invention
The present invention relates to a multi-speed transmission.
2. Description of the Related Art
One known example of this type of a transmission is a so-called dual-clutch transmission (DCT) described below (see, for example, Japanese Unexamined Patent Application Publication No. 2005-172220). A DCT includes two input shafts of first and second input axes to which power is transferred from a driving source using two clutches of first and second clutches, respectively, and two output shafts of first and second output shafts each being provided with an output gear meshing with a differential gear. In the DCT, a driving gear of an odd-numbered gear train in order of the transmission gear ratios is fixed to the first input shaft, and a driving gear of an even-numbered gear train in order of the transmission gear ratios fixed to the second input shaft. In the DCT, a driven gear meshing with a driving gear of each of a plurality of lower-speed gear trains is supported by the first output shaft, and a driven gear meshing with a driving gear of each of a plurality of higher-speed gear trains is supported by the second output shaft. The driven gears on the first and second output shafts are selectively coupled to the respective output shafts using a synchromesh mechanism.
For this type of a transmission, in power transfer using an odd-number gear train in order of the transmission gear ratios (at this state, the first clutch is engaged, whilst the second clutch is disengaged), the driven gear of an even-numbered gear train can be coupled to its corresponding output shaft using the synchromesh mechanism. Therefore, disengagement of the first clutch and engagement of the second clutch in transmission can responsively switch the state to a power transfer state through the even-numbered gear train.
Similarly, in power transfer using an even-number gear train in order of the transmission gear ratios, the driven gear of an odd-numbered gear train can be coupled to its corresponding output shaft using the synchromesh mechanism, and disengagement of the second clutch and engagement of the first clutch in transmission can responsively switch the state to a power transfer state through the odd-numbered gear train.